FAULT-TOLERANCE THROUGH SCHEDULING OF APERIODIC TASKS IN HARD REAL-TIME MULTIPROCESSOR SYSTEMS

Real-time systems are being increasingly used in several applications which are time critical in nature. Fault-tolerance is an important req uirement of such systems, due to the catastrophic consequences of not tolerating faults. In this paper, we study a scheme that provides faul t-tolerance through scheduling in real-time multiprocessor systems. We schedule multiple copies of dynamic, aperiodic, nonpreemptive tasks i n the system, and use two techniques that we call deallocation and ove rloading to achieve high acceptance ratio (percentage of arriving task s scheduled by the system). This paper compares the performance of our scheme with that of other fault-tolerant scheduling schemes, and dete rmines how much each of deallocation and overloading affects the accep tance ratio of tasks. The paper also provides a technique that can hel p real-time system designers determine the number of processors requir ed to provide fault-tolerance in dynamic systems. Lastly, a formal mod el is developed for the analysis of systems with uniform tasks.